Changed CP detection algorithm

lte/phy/include/liblte/phy/common/phy_common.h

@@ -65,12 +65,12 @@ typedef enum {CPNORM, CPEXT} lte_cp_t;
 #define SYMBOL_SZ_MAX   2048
 
 #define CPNORM_NSYMB    7
-#define CPNORM_SF_NSYMB 2*CPNORM_NSYMB
+#define CPNORM_SF_NSYMB (2*CPNORM_NSYMB)
 #define CPNORM_0_LEN    160
 #define CPNORM_LEN      144
 
 #define CPEXT_NSYMB     6
-#define CPEXT_SF_NSYMB  2*CPEXT_NSYMB
+#define CPEXT_SF_NSYMB  (2*CPEXT_NSYMB)
 #define CPEXT_LEN       512
 #define CPEXT_7_5_LEN   1024
 
@@ -78,13 +78,13 @@ typedef enum {CPNORM, CPEXT} lte_cp_t;
 #define CP_ISEXT(cp) (cp==CPEXT)
 #define CP_NSYMB(cp) (CP_ISNORM(cp)?CPNORM_NSYMB:CPEXT_NSYMB)
 
-#define CP(symbol_sz, c) (c*symbol_sz/2048)
-#define CP_NORM(symbol, symbol_sz) (symbol==0)?CP(symbol_sz,CPNORM_0_LEN):CP(symbol_sz,CPNORM_LEN)
-#define CP_EXT(symbol_sz) CP(symbol_sz,CPEXT_LEN)
+#define CP(symbol_sz, c) ((c*symbol_sz)/2048)
+#define CP_NORM(symbol, symbol_sz) ((symbol==0)?CP((symbol_sz),CPNORM_0_LEN):CP((symbol_sz),CPNORM_LEN))
+#define CP_EXT(symbol_sz) (CP((symbol_sz),CPEXT_LEN))
 
 #define SLOT_LEN(symbol_sz)     (480*((symbol_sz)/64))
 #define SF_LEN(symbol_sz)       (2*SLOT_LEN(symbol_sz))
-#define SF_LEN_MAX              SF_LEN(SYMBOL_SZ_MAX)
+#define SF_LEN_MAX              (SF_LEN(SYMBOL_SZ_MAX))
 
 #define SLOT_LEN_RE(nof_prb, cp)        (nof_prb*RE_X_RB*CP_NSYMB(cp))
 #define SF_LEN_RE(nof_prb, cp)          (2*SLOT_LEN_RE(nof_prb, cp))

lte/phy/lib/sync/src/sync.c

@@ -143,9 +143,41 @@ lte_cp_t sync_get_cp(sync_t *q) {
   return q->cp;
 }
 
-static lte_cp_t detect_cp(cf_t *input, uint32_t peak_pos) 
+/* CP detection algorithm taken from: 
+ * "SSS Detection Method for Initial Cell Search in 3GPP LTE FDD/TDD Dual Mode Receiver"
+ * by Jung-In Kim et al. 
+ */
+static lte_cp_t detect_cp(sync_t *q, cf_t *input, uint32_t peak_pos) 
 {
-  return CPNORM;
+  float R_norm, R_ext, C_norm, C_ext; 
+  float M_norm, M_ext; 
+  
+  R_norm = crealf(vec_dot_prod_conj_ccc(&input[peak_pos-q->fft_size-CP_NORM(7, q->fft_size)], 
+                                        &input[peak_pos-CP_NORM(7, q->fft_size)], 
+                                        CP_NORM(7, q->fft_size)));    
+  C_norm = cabsf(vec_dot_prod_conj_ccc(&input[peak_pos-q->fft_size-CP_NORM(7, q->fft_size)], 
+                                       &input[peak_pos-q->fft_size-CP_NORM(7, q->fft_size)], 
+                                       CP_NORM(7, q->fft_size)));
+  R_ext  = crealf(vec_dot_prod_conj_ccc(&input[peak_pos-q->fft_size-CP_EXT(q->fft_size)], 
+                                        &input[peak_pos-CP_EXT(q->fft_size)], 
+                                        CP_EXT(q->fft_size)));
+  C_ext  = cabsf(vec_dot_prod_conj_ccc(&input[peak_pos-q->fft_size-CP_EXT(q->fft_size)], 
+                                       &input[peak_pos-q->fft_size-CP_EXT(q->fft_size)], 
+                                       CP_EXT(q->fft_size)));
+  M_norm = R_norm/C_norm;
+  M_ext = R_ext/C_ext;
+
+  if (M_norm > M_ext) {
+    return CPNORM;    
+  } else if (M_norm < M_ext) {
+    return CPEXT;
+  } else {
+    if (R_norm > R_ext) {
+      return CPNORM;
+    } else {
+      return CPEXT;
+    }
+  }
 }
 
 int sync_sss(sync_t *q, cf_t *input, uint32_t peak_pos) {
@@ -156,7 +188,7 @@ int sync_sss(sync_t *q, cf_t *input, uint32_t peak_pos) {
   sss_synch_set_N_id_2(&q->sss, q->N_id_2);
 
   if (q->detect_cp) {
-    q->cp = detect_cp(input, peak_pos);
+    q->cp = detect_cp(q, input, peak_pos);
   }
   
   /* Make sure we have enough room to find SSS sequence */
@@ -184,7 +216,8 @@ int sync_sss(sync_t *q, cf_t *input, uint32_t peak_pos) {
   return 1;
 }
 
-int sync_find(sync_t *q, cf_t *input, uint32_t find_offset, uint32_t *peak_position) {
+int sync_find(sync_t *q, cf_t *input, uint32_t find_offset, uint32_t *peak_position) 
+{
   
   int ret = LIBLTE_ERROR_INVALID_INPUTS; 
   

lte/phy/lib/ue/src/ue_celldetect.c

@@ -211,7 +211,7 @@ int ue_celldetect_scan(ue_celldetect_t * q,
     for (uint32_t nf=0;nf<nof_input_frames;nf++) {
       sync_set_N_id_2(&q->sfind, q->current_N_id_2);
 
-      DEBUG("[%3d/%3d]: Searching cells with N_id_2=%d. %d frames\n", 
+      printf("[%3d/%3d]: Searching cells with N_id_2=%d. %d frames\n", 
            q->current_nof_detected, q->current_nof_total, q->current_N_id_2, nof_input_frames);
 
       /* Find peak and cell id */